The present invention relates generally to gear pumps, and more particularly to a sanitary design gear pump in which two gear shaft bearing blocks constitute hand removable structural end bodies of the pump.
Among the many types of known rotary positive displacement pumps, gear pumps constitute an old and well developed patent and commercial art. Gear pumps are most frequently found in the patent art and commercial practice as liquid transfer devices and as pressure pumps for hydraulic systems. They are well characterized as to their relative pumping virtues as well as their limitations in application and use. Gear pumps are also employed and well understood as metering pumps and more recently as dosing, dispensing or liquid filling pumps. For example, Oden Corporation of Buffalo, N.Y., USA manufactures a liquid filling machine product known as SERVO/FILLe which now uses the gear pump of the present invention coupled to a servo controlled motor to define a liquid dose or fill volume based upon the amount of rotation of the gear pump, the flow rate being determined by the rate of rotation of the pump.
Among the applications for rotary positive displacement pumps are the so-called sanitary markets. These include pharmaceutical, biomedical, food, personal care and cosmetics and the like. These sectors are largely served by only a few types of rotary sanitary pumps.
One type is termed a sanitary externally timed rotary lobe pump. This type of rotor pump has an external gearbox which times or positions pump rotors such that they rotate in correct relationship with one another within a pump housing. The rotors are non-contacting but in close tolerance to each other. A variation on this rotor pump type is known as a circumferential piston pump. In either case, these pumps are very expensive by virtue of their complexity and extensive and robust construction requirements. An example of this type of pump is the Universal Series as manufactured by Waukesha Cherry-Burrell of Delavan, Wis., USA.
Another type of rotary positive displacement sanitary pump is termed a Sine pump (U.S. Pat. No. 4,575,324) as manufactured by Sine Pump of Arvada, Colo., USA. The sanitary Sine pump uses a sine wave shaped rotor running through a sliding gate such that a positive pumping action is created. This pump type is very expensive because of the complex shape of the rotor, the close tolerances, robust construction and the expensive materials utilized in its construction.
Still another type of sanitary rotary positive displacement pump is the progressing cavity type as manufactured, for example, by Moyno Industrial Products of Springfield, Ohio, USA. The progressing cavity pump uses a complex helix-like rotor running in close contact and tolerance to a progressing cavity shaped stator. These sanitary pumps are, like the other common types, very expensive by virtue of their complex structures, expensive materials of construction and robust design requirements.
Regardless of the sanitary rotary positive displacement pump type, certain common characteristics can be noted. Among these are an ability to rapidly tear down or open the fluid flow pathway of the pump for easy and thorough inspection and cleaning, often without the need for tools; the extensive use of stainless steels to assure non-contaminating and non-corroding liquid pumpage contact surfaces; the use of simple sanitary seal structures; the minimization or elimination of areas within the interior of the pump which could cause contamination of the pumpage; low RPM operation for gentle liquid handling; ability to operate at elevated temperatures; an ability to pump liquids ranging from very low viscosity to very high viscosity; and conformance to generally recognized sanitary standards, particularly the Standards For Centrifugal and Positive Rotary Pumps For Milk and Milk Products, 0-09, as promulgated in the US by the 3-A Sanitary Standards Symbol Administrative Council. This standard, which appears as Appendix A to this application, applies not only to dairy uses but also is the de facto standard for most sanitary pump uses.
Notably absent from rotary positive displacement sanitary pump types are gear pumps. This is true in terms of commercial art, and relatively few examples are found in the prior patent art. This may be generally the case because available industrial service (non-sanitary) gear pumps are not designs which are acceptable or easily adaptable for sanitary service. This is also the case even though many such otherwise suitable industrial gear pumps are available with the major fluid flow components such as the pump body, shafts and gears fabricated from materials appropriate to sanitary use, such as stainless steel.
Even though sanitary versions of gear pumps are not generally known in commercial practice, it is nevertheless true that industrial service gear pumps are often used in sanitary applications even though such pumps do not meet generally accepted sanitary standards or regulatory statutes and requirements. This is the case because the gear pump design unto itself is broadly competent in pumping many sanitary liquids, but is much less expensive than true sanitary rotary positive displacement designs available in the marketplace. For one comparative example, a 316 stainless steel industrial gear pump costs less than 33% of the price of the most widely used externally timed sanitary rotary circumferential piston pump of equivalent pumping capability.
It is also widely understood that industrial service (non-sanitary) gear pumps are often used in sanitary applications requiring critical metering or dosing capabilities, these being applications for which precision gear pumps can be more suited than other types of sanitary positive displacement pumps. It is also generally understood that where low or very low flow rates are required, sanitary positive displacement designs are generally commercially unavailable.
It is also to be noted that among knowledgeable and experienced designers of sanitary devices, equipment and pumps there has long been held the general opinion that the external gear type pump is unsuitable for sanitary service and applications because the bearings which support each gear shaft are usually internal to the pump and in contact with the liquid being pumped. This leads to concerns regarding bearing materials suitable to sanitary liquids, and further to the ease of access and cleanability and inspectability of the bearings, which almost always have a depth much greater than diameter or shaft bore.
Because of the limitations presented by sanitary service rotary positive displacement pumps of known type, which are principally economic, and because of the technical and economic need for a gear pump which satisfies and meets the requirements for sanitary service, it is the primary objective of this disclosure to present and describe a unique and novel gear pump of sanitary design. In this regard it is important to note that there are a wide array of uses of gear pumps in general industrial and non-sanitary applications of every type and nature. In many such applications, a gear pump such as that herein disclosed capable of rapid tear down without tools, easy cleaning and inspection, and constructed of corrosion resistant materials, can provide important advantages for rapid changeover of pumpage, elimination of contamination and substantially improved pump productivity. The detailed and numerous particular objects of this invention are set forth further on in this specification.
Numerous rotary positive displacement sanitary pump designs have been set forth in the prior patent and commercial art. The most prominent characteristics of several are herein reviewed by way of technical background.
Dale and Reed (U.S. Pat. No. 2,635,552) teach an externally timed rotary positive displacement rotor pump particularly designed for sanitary service, the pump being provided with studs and wing nuts for rapid removal of the pump housing without tools, and with dowel pins for precision alignment. However, removal of the pumping gears requires the use of tools.
Maisch (U.S. Pat. No. 2,909,124) discloses a gear pump having a housing consisting of three metal discs, aligned by dowel pins and sealed one to the other by O-rings, the pump being particularly designed for sanitary service by virtue of its ease of assembly and disassembly, without the use of tools. In the Maisch disclosure, the driven gear rotates on a fixed shaft and the drive shaft seal is an elastomeric element positioned into a cavity formed by the mating of the center pump body disc and the backing plate disc.
Werra (U.S. Pat. No. 3,291,059) teaches an externally timed rotary positive displacement rotor pump particularly designed for sanitary service, the pump having an ability to be readily disassembled by removal of the pump housing parts from studs, the housing parts being secured by hand removable retaining nuts. Werra further discloses pump impellers which xe2x80x9cfloatxe2x80x9d on splined shafts within the pumping cavity thus allowing ready removal from the pump without the use of tools, the impellers being made from a special non-galling high copper alloy, the alloy having a low coefficient of expansion thus allowing close tolerances of the rotors to the pump housing.
Hiroyoki and others (JP 60019976) disclose a gear pump designed to facilitate cleaning. The pump is designed such that the release and removal of a bevel face clamp allows separation of the pump into two sections. One section consists of the pump housing together with the non-drive end gear shaft support bearings. This first section moves outward and away from the drive end of the pump on a set of guides associated with the elevated surface upon which the pump is mounted. The second section consists of the pump gears, the drive end gear support bearings and the drive gear shaft seal assembly. The second section remains fixed to the pump drive assembly by a drive gear shaft coupling member.
Morita and Yamamoto (U.S. Pat. No. 5,370,514) teach an externally timed rotary positive displacement rotor pump designed for sanitary pumping applications in which the pump rotors are fitted to hollow drive shafts and fastened by a long bolt from the drive end of the pump, thus allowing the faces of the pumping rotors to be flat and thereby eliminating any rotor-to-shaft fastener on the face of the rotors. The use of flat-faced rotors eliminates a trap zone within the pump thus improving the sanitary characteristics of the design.
In the prior commercial art, Waukesha Cherry-Burrell of Delavan, Wis. discloses, in a publication entitled xe2x80x9cUG Series Gear Pumpsxe2x80x9d (95-03030, effective October 1998), a gear pump in which the gear shaft support bearings are rolling element bearings which are external to the pump fluid flow pathway, each of the four gear shafts being sealed by a mechanical seal at the point where each shaft penetrates the pump housing. This design results in a fluid flow pathway of minimal liquid volume which is more easily flushed and cleaned in situ, that is without pump disassembly. The pump is thus particularly designed as a clean-in-place device and is not suited for easy or rapid disassembly for cleaning or inspection.
Also in the prior commercial art, Oden Corporation has utilized a gear pump provided by its subsidiary, Niagara Pump Corporation, as a dosing pump in its liquid filling machines. This pump represents a substantial improvement over industrial gear pump designs in terms of incorporation of elements of sanitary design. However, it does not present a complete solution or one that is in compliance as a sanitary pump to the specifications of and design requirements of the 3-A Sanitary Standards Symbol Administrative Council (US) Standard Number 0-09 xe2x80x9cStandards for Centrifugal and Positive Rotary Pumps for Milk and Milk Products.xe2x80x9d
In order to allow and ensure accurate comparison of the cited commercial prior art consisting of the Niagara Pump Corporation provided gear pump utilized by Oden Corporation in its liquid filling machines to the pump of the present invention, Figures showing this prior art are included in this specification. These figures provide a complete and accurate representation of the prior art pump.
It is the primary object of the present invention to overcome the numerous disadvantages and limitations, as set forth above, of the presently known sanitary rotary positive displacement pumps, and to set forth the unique and novel specifications for a sanitary gear pump.
More specifically, the particular and detailed objects of the present invention include:
1. To disclose a unique and novel rotary positive displacement gear pump fully complying with the sanitary design requirements of the 3-A Sanitary Standards Symbol Administrative Council (US) Standard Number 0-09 xe2x80x9cStandards for Centrifugal and Positive Rotary Pumps for Milk and Milk Products.xe2x80x9d
2. To disclose a unique and novel rotary positive displacement sanitary gear pump capable of being offered to the commercial market for a price of no more than fifty to sixty percent of the price of an equivalent sized sanitary pump of prior embodiment.
3. To disclose a unique and novel sanitary gear pump in which the structural end bodies of the pump are the bearing structures, termed bearing blocks, bearing bodies, bearing liners, end liners, or liners, which are used to support and position the pump gears and gears shafts, wherein the gear support bearings are through holes completely piercing the bearing blocks, thus allowing facilitated cleaning and inspection and elimination of any possible trap zones as found in blind hole bearings.
4. To disclose a unique and novel sanitary gear pump in which the through hole bearings are end sealed using seal rings and a simple seal plate applied against the outer face of the bearing block. The seal rings can be of essentially any type including gaskets, flat ring, O-ring, Vee ring, U-cup and the like. The clamp plate can also be termed an end plate, a seal plate, a liner end cap, or a retainer plate.
5. To disclose a unique and novel sanitary gear pump in which the static gear shaft seal ring glands located on the outside face of the bearing blocks are sized to grip the seal rings during the pump assembly process thereby easing and simplifying pump assembly.
6. To disclose a unique and novel sanitary gear pump in which the through hole bearing design allows the bearing length to be much longer than the gear shaft diameter without impairment of cleanability of the device.
7. To disclose a unique and novel sanitary gear pump in which the bearing block to body seal arrangement allows seal disengagement immediately upon the start of withdrawal of the bearing block from the pump, thus greatly easing hand or manual pump disassembly by reducing and breaking the vacuum formed by such bearing block withdrawal.
8. To disclose a unique and novel sanitary gear pump in which the length of the pumping cavity is defined by the distance between the face of pilot portions of opposed bearing blocks, which pilot portions are received in each end of the gear cavity bore when fully assembled.
9. To disclose a unique and novel sanitary gear pump in which the bearing blocks comprising the structural end bodies of the pump extend into the gear cavity bore of the pump only to the degree necessary to form two sides of a seal ring gland and capture and align the bearing blocks and gears coaxially within the pump.
10. To disclose a unique and novel sanitary gear pump in which gear cavity bore end seals arranged in a gland immediately adjacent but external to the end of the net bore shape of the gear cavity bore maximizes the bearing block to pump body direct contact square area thereby maximizing the assembled pump""s dimensional accuracy, stability and durability.
11. To disclose a unique and novel sanitary gear pump in which the square area of the circular flange-like face to face engagement of the bearing blocks and pump body is maximized by the gear cavity bore to bearing block seal placement, thus substantially reducing the possibility during pump assembly of over-tightening the bearing blocks into the gear cavity bore of the pump, thus assuring that a correct and defined distance is established and repeatably maintained between the pump bearings and the pump gear faces, regardless of assembly clamping force.
12. To disclose a unique and novel sanitary gear pump in which the bearing block to gear cavity bore seal arrangement minimizes the pump assembly mating force required to correctly compress each seal ring in the pump.
13. To disclose a unique and novel sanitary gear pump in which the end body bearing blocks enter into the gear cavity bore of the pump for a distance that is approximately equivalent to the diameter of the bearing to body seal element for the longest gears which may be received by the gear cavity bore.
14. To disclose a unique and novel sanitary gear pump in which the bearing block to gear cavity bore seal arrangement allows bearing block to pump body assembly free of seal ring rolling, cutting, or distortion and without risk of the seal ring becoming unseated from its gland.
15. To disclose a unique and novel sanitary gear pump in which the bearing block to gear cavity bore seal arrangement increases the ability of the bearing blocks to resist dimensional distortion due to cold flow.
16. To disclose a unique and novel sanitary gear pump in which the bearing block to gear cavity bore seal arrangement confers the ability of the non-drive end bearing block to be assembled into the pump body such that rotation to correct orientation and seating is signified by both a perceptible audible and a perceptible tactile telltale.
17. To disclose a unique and novel sanitary gear pump in which the thermal expansion of the bearing blocks with increasing pump temperature results in dimensional increase predominantly to the portion of the block outside of the gear cavity bore thus allowing a usable gear face to bearing face tolerance to be maintained without contact over a useful temperature range of at least 270xc2x0 F.
18. To disclose a unique and novel sanitary gear pump in which the bearing block to gear cavity bore arrangement prevents pumped liquid from coming into contact with the flange faces of the pump body and bearing blocks, thus eliminating a liquid trap and contamination zone, thus enhancing the sanitary design of the pump.
19. To disclose a unique and novel sanitary gear pump in which the seal glands located at the ends of the gear cavity bore are established, formed and defined by the gear cavity bore and bearing block such that the seal element within the gland is properly and repeatably compressed when the bearing block is installed and clamped into the pump body, but cannot be overcompressed because of the bearing block face to pump bore face engagement method.
20. To disclose a unique and novel sanitary gear pump in which the drive gear dynamic shaft seal arrangement is comprised of a single cartridge assembly which is removed from and installed onto its shaft by manually gripping or grasping a flange or grip or groove constituting the external end structure of the seal cartridge. The seal cartridge assembly may also be alternatively and equivalently termed the seal assembly, the seal gland, the seal assembly housing or the seal can.
21. To disclose a unique and novel sanitary gear pump in which the drive gear dynamic seal cartridge is retained in and sealed to the bearing block by a static seal ring and a simple shaft seal clamp plate applied against a flange on the seal cartridge and the outer face of the bearing block, the clamp plate being held in place by the pump assembly means. The stationary seal rings can be of essentially any type, including gasket, flat ring, O-ring, Vee ring, U-cup and the like.
22. To disclose a unique and novel sanitary gear pump in which the drive gear dynamic shaft seal assembly allows interchangeable use of numerous dynamic drive gear shaft seal methods including square ring, quad ring, O-ring, Vee ring, U-cup, internal mechanical, external mechanical and packing seals, all types using the same circumferential cartridge to bearing block seal ring, and retaining the same seal housing outside diameter.
23. To disclose a unique and novel sanitary gear pump in which the drive gear dynamic shaft seal assembly means precludes leakage resulting from a change in seal assembly position or location when the pump is in assembled condition.
24. To disclose a unique and novel sanitary gear pump in which the drive gear dynamic shaft seal assembly is prevented from rotating by locking male and female D-shaped elements on the seal housing and seal clamp plate respectively.
25. To disclose a unique and novel sanitary gear pump in which the pump body orientation in the pump mount is precisely established and maintained by a simple and robust pin and groove arrangement, such that four locator slots or channels are provided at ninety degree intervals at the drive end of the pump body, each slot being shaped to provide a contoured or tapered guide for easy engagement with the mating pin. The mating pin is located in the pump mount and allows selection of pump port orientation in any of four possible locations, at ninety degree intervals of rotation.
26. To disclose a unique and novel sanitary gear pump in which the pump mount consists of a fixed cylindrical element into which the drive end bearing block and a portion of the pump body inserts for precise and repeatable orientation and location. The mount has integral pump assembly binding tie rods (also termed draw bars) and the mount foot is reverse of the cylinder portion in an xe2x80x9copen Zxe2x80x9d form, thus allowing a fully overhung pump mount in which the pump ports are unobstructed by the mount.
27. To disclose a unique and novel sanitary gear pump in which the pump mount, when aligned to a pump drive, allows the pump to be repeatedly removed from the mount and reinstalled into the mount without any loss of or change in pump to drive alignment. The pump to mount engagement means further allows the removal of pump from any given mount and replacement by any other pump of the same model into the mount without any loss of pump-mount-drive alignment.
28. To disclose a unique and novel sanitary gear pump in which the pump is attached to its mount by use of two tie rods one of which carries a captured cross bar which swings across to and engages with the second tie rod, a single hand operated threaded fastener (termed the adjustment screw, the assembly screw, or the binder screw), this element then being tightened upon the center of the non-drive end seal plate to effect complete pump assembly, sealing and location, all without the need for or use of tools of any sort.
29. To disclose a unique and novel sanitary gear pump in which the assembly of the pump bearing blocks, pump gears and pump body as well as the assembly of the drive gear shaft dynamic seal assembly as well as the mounting and sealing of all constituent pump components is achieved with a single hand operated fastener device.
30. To disclose a unique and novel sanitary gear pump in which the pump assembly hardware remain captured and attached to the integral pump mount when the pump is in a disassembled condition.
31. To disclose a unique and novel sanitary gear pump in which the centered application of binding force by the single threaded clamping fastener acting on binding bars attached to the pump mount assures that a truly centered and balanced coaxial assembly force is applied through the entire pump structure.
32. To disclose a unique and novel sanitary gear pump in which the pump assembly may be automatically sealed and retained in its mount using hydraulic, pneumatic or motor driven means, with electronic sensing of status.
33. To disclose a unique and novel sanitary gear pump in which the spline coupling drive shaft design in combination with the pump mount allows removal of the pump from its mount without the requirement to remove any shaft to drive coupling. The splined gear drive shaft also allows the drive gear to be removed from the pump without the requirement to remove any drive coupling.
34. To disclose a unique and novel sanitary gear pump in which the use of different shaft diameters for the drive and driven gears precludes incorrect assembly of the pump.
35. To disclose a unique and novel sanitary gear pump in which the use of different length bearing blocks for the drive and non-drive pump ends precludes incorrect assembly of the pump.
36. To disclose a unique and novel sanitary gear pump in which the bearing block design allows reconfiguration of the pump at any time to vary displacement by simple and economical substitution of gears of alternate length along with the drive end bearing block of appropriate corresponding length.
37. To disclose a unique and novel sanitary gear pump in which the pump may be readily reconfigured to vary displacement by the simple substitution of gears of alternate length in combination with a pump body of appropriate corresponding length, the bearing blocks of the pump remaining unchanged.
38. To disclose a unique and novel sanitary gear pump in which the spline end of the drive gear shaft is reduced in diameter to be less than the diameter of the shaft in the pump shaft seal area with a smooth tapered transition between the two diameters for the purpose of assuring simple and easy seal installation onto and removal from the shaft with lowered risk of damage to the shaft seal element.
39. To disclose a unique and novel sanitary gear pump in which the drive gear shaft can be particularly hardened to withstand the wear effects exerted upon the shaft by rotation against a shaft sealing ring, U-cup, Vee ring, or packing or similar seal arrangement.
40. To disclose a unique and novel sanitary gear pump in which the minimal penetration of the pump gear bearings into the gear cavity bore of the pump greatly reduces the circumferential leakage pathway between the bearing blocks in the gear cavity bore and the wall of the gear cavity bore.
The foregoing objects of this invention, as well as other objects and advantages of this invention, will be more fully appreciated after a consideration of the following detailed description taken in conjunctions with the accompanying drawings in which a preferred form of this invention is illustrated.